Silver halide color photographic elements, based on the three primary (i.e., yellow, magenta and cyan) color principle of the subtractive color process, are substantially composed of at least one blue-sensitive (or blue-sensitized) silver halide emulsion layer which is colored (upon color processing) yellow by the action of blue (from 400 to 500 nm) light, at least one green-sensitized silver halide emulsion layer which is colored (upon color processing) magenta by the action of green (from 500 to 600 nm) light, and at least one red-sensitized silver halide emulsion layer which is colored (upon color processing) cyan by the action of red (from 600 to 700 nm) light.
It is well known that cyan, magenta and yellow image dyes are formed by the imagewise coupling reaction of oxidized aromatic primary amino developing agents with color-forming compounds or couplers. Usually, phenol or naphthol couplers are used to form the cyan dye image; 5-pyrazolone, pyrazolotriazole or pyrazolobenzimidazole couplers are used to form the magenta dye image; and open-chain ketomethylene couplers are used to form the yellow dye image.
Ideally, in such color photographic elements, the yellow dye image formed absorbs blue light only, the magenta dye image absorbs green light only, and the cyan dye image absorbs red light only.
Unfortunately, the absorption spectra of conventional dyes formed from the color-forming couplers are never "clean". Thus, the cyan dye, which should absorb red light and transmit green and blue light, usually absorbs a considerable amount of green and blue light as well as a major proportion of the red light.
As a means for removing such unwanted absorption, i.e., absorption at wavelengths lower than about 600 nm, there is generally practiced in the art the so called masking method, in which a colored image forming coupler (namely colored masking coupler) is used in addition to the cyan image-forming coupler that is to be color corrected, as described in detail in J. Phot. Soc. Am. 13, 94 (1947), J. Opt. Soc. Am. 40, 166 (1950) or J. Am. Chem Soc. 72, 1533 (1950). The colored masking coupler absorbs both green and blue light and is capable of reacting with oxidized color developer (during the color development processing step) to yield the cyan image dye while simultaneously losing its ability, in proportion to development, to absorb in the green and blue regions of the spectrum, thereby correcting for the unwanted green and blue absorption of the cyan dye derived from the main cyan dye-forming coupler in the photographic element.
Usually, to correct the unwanted absorption of the cyan image-dye, phenol or naphthol couplers are used which are colored by virtue of containing a chromophore group which is split off or destroyed during and by means of the coupling reaction with the result that the original color of the colored coupler is destroyed and a cyan dye is formed upon coupling. Colored cyan dye-forming couplers are described, for instance, in U.S. Pat. Nos. 2,449,966, 2,453,661, 2,445,169, 2,455,170, 2,521,908, 2,706,684, 3,476,563, 4,004,929, 4,138,258, and 4,458,012.
A second problem with silver halide multilayer color photographic elements is that sensitizing dyes used for spectrally sensitizing silver halide emulsions to red light exhibit a relatively broad absorbance spectrum which gives to the red sensitized silver halides unwanted sensitivity (during exposure) in spectral regions other than that of the red light, namely in the spectral region of green light, thus resulting in poor color separation between the green sensitive (magenta) layer and the red sensitive (cyan) layer. Use of large quantities of the above described cyan dye-forming colored masking couplers, which have a main absorption in the wavelength region of about 500 to 600 nm, reduces this unwanted absorption of the sensitizing dyes for the cyan layer, especially if these cyan dye-forming colored masking couplers are in an intermediate lawyer between the magenta and the cyan layers and/or in the upper cyan layer of the photographic element. This method may be not wholly satisfactory since the use of excessive quantities of cyan dye-forming colored masking couplers can lead to sensitivity loss in the magenta layer and/or inferior color rendition by over-correcting the color reproduction through excessive use of the masking function.
Despite all of the efforts practiced in the art, however, a fully adequate degree of color separation has not been attained by the above masking methods as desired for a multilayer color photographic element. There is a need to provide a multilayer color photographic element showing improved color separation.
Magenta colored azo dyes comprising water soluble groups and hydrophobic groups have been described as bleaching dyes for photothermographic recording materials in JP 59-184,340 and JP 61-120,143, as dyes for ink jet recording in JP 93-80,955, as light fast dyes in Zhur. Priklad. Khim., 33, 1617-23 (1960), and as dyes for the construction of optical devices in GB 2,204,053.
WO 91/06037 describes a photographic material comprising a non-diffusible yellow and a non-diffusible magenta azomethine dye in an interlayer between a fast cyan layer and a slow magenta layer.
EP 550,109 describes a silver halide color photographic material comprising a water soluble magenta-colored azo dye in a magenta layer.